1. Field of the Invention
The invention relates to a method for determining the amount of laundry in an at least approximately horizontally supported drum for laundry being drivable by a universal motor at a washing and drying rpm, on the basis of observations of parameters of an operation in a laundry handling machine.
Such methods are known from German Published, Non-Prosecuted Applications DE 30 30 491 and 33 29 345. In those methods, in order to determine the amount of laundry, or the amount of water needed to wash that amount of laundry, the inflow time between two certain level marks in the wash water holder are measured and a conclusion is drawn therefrom as to the final amount of water required. That method is very inaccurate, because both the water pressure prevailing upstream of the magnet valve and the quantity controller located in the magnet valve as well as the water level transducer or transducers, each involve tolerances, which can even add up in the least favorable case. That kind of quantity determination can also be carried out only once in the entire process of laundry handling, namely during the first time that water flows in and during the thus-effected wetting of the laundry.
In order to eliminate those inaccuracies, it has already been proposed to determine the inflowing amount of water by means of a water meter (German Published, Non-Prosecuted Application DE 29 21 911) or by counting out the refill processes needed during the phase of wetting the laundry (German Published, Non-Prosecuted Application DE 34 46 288). Besides the increased effort and expense to achieve accurate determination of the amount of water or laundry, that determination is again possible only once during the handling cycle.
Since the differentiated determination of the amount of laundry can be of great significance for the selection and form of the next handling cycle to be run, there is a need to achieve the most accurate possible determination of the amount of laundry.
2. Summary of the Invention
It is accordingly an object of the invention to provide a method for determining the amount of laundry in a laundry handling machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and which improves the accuracy of such a method, if at all possible at no added engineering effort or expense.
With the foregoing and other objects in view there is provided, in accordance with the invention, in a method for determining an amount of laundry in an at least approximately horizontally supported drum for laundry being driven by a universal drive motor at a washing and drying rpm, on the basis of observations of parameters of an operation in a laundry handling machine, the improvement which comprises determining a drive moment at the drum drive motor during a drum startup phase, for operating the drum at a controlled handling rpm at which the laundry is not held against a wall of the drum by centrifugal force.
The drum drive moment is a direct image of the load moment generated by the loaded laundry drum, which is caused directly after the drum drive motor is turned on, because of a brief load peak resulting from high mass inertia, and as the process continues it is caused by the rising of the load of laundry from the lowest point of the drum, possibly under the influence of driver protrusions inside the drum. Different sizes of laundry loads naturally cause various magnitudes of load moment, which must be overcome by variously high drive moments.
Therefore, the drive moment is directly dependent on the mass of laundry to be moved in the drum. Through the use of suitable calculation methods, a microcomputer can determine therefrom the value of the laundry mass with sufficient accuracy. Engineering effort need not be employed further for this, since the drive moment can be calculated from the electrical data of the motor control, including the constants of the motor itself.
In accordance with another mode of the invention, given phase lead control for the drive motor, during the drum startup phase, a phase lead angle is recorded continuously and its geometrical mean value is formed, which is a gauge for a mean output of the drive motor, from which a mass of the load of laundry is calculated through a mass inertia and the load moment of the load of laundry. With the typical use of microprocessors, computer capacity is also already available for other control tasks and need merely be installed by suitable programming. The mean value formation is highly suitable as a basis for calculating the mass of the load of laundry.
In accordance with a further mode of the invention, in a washing machine equipped with a device for ascertaining the amount of water in the wash water holder, information about the amount of water located in the wash water holder is an excellent correction value for calculating the mass.
In accordance with an added mode of the invention, values about possible rpm deviations from the command value for the rpm rise are recorded and taken into account by calculating the mass. This is especially advantageous because pieces of laundry tumbling in the drum even in the startup phase occasionally can drop onto a driver protrusion which is just then entering the path by which the laundry drops and as a result can generate an additional load moment.
In accordance with an additional mode of the invention, a profile of rpm deviations is evaluated (periodically, singularly, flatly, abruptly, etc.), and depending on the evaluation, the profile is associated with a memorized attribute about the nature of the load of laundry (large, average, small, absorbent, not so absorbent items of laundry, etc.), then other characteristics of the load of laundry resting in the drum can be detected and used to configure the just-started handling cycle.
In accordance with yet another mode of the invention, a device for determining the magnitude of an operating voltage of the drive motor is a variable which is taken into account as a correction value in calculating the mass. This makes it possible to preclude inaccuracies that would arise from mains voltage fluctuations, regardless of the nature of the measurement method.
In accordance with yet a further mode of the invention, in a drum-type clothes dryer, in the beginning and in the course of the drying cycle, the drive moment at the drum drive is determined multiple times and used to calculate the mass of the particular load of laundry, and differences between successive findings from calculations are used as a gauge for determining the residual moisture of the load of laundry just at that moment.
In accordance with yet an added mode of the invention, as a result, a drying process can be controlled in some way or other as a function of the residual moisture value and finally when the desired goal is reached it can be discontinued.
In accordance with a concomitant mode of the invention, in order to further increase the accuracy of determining the mass of laundry, during an rpm holding phase following the drum startup phase, the mean phase lead angle of the rpm control device of the drum drive motor can be ascertained and serves as a gauge for machine-dictated braking moments to be taken into account in the mass determination by means of the phase lead angle of the startup phase. Such braking moments can be caused by laundry friction, by flexing work of the drum drive belt, by bearing friction, and by other machine-dictated causes.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for determining the amount of laundry in a laundry handling machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.